To further improve integration degrees of semiconductors such as of a large scale integration (LSI), it is desired to make finer patterns during productions of semiconductors, and currently the smallest pattern size is 100 nm or shorter.
Formations of such fine patterns in semiconductor devices have been realized by shortening wavelength of light from a light source of exposure devices and improving resist materials. Currently, formations of fine patterns have been performed by a liquid immersion lithography, in which exposure is performed through water with a light source that emits argon fluoride (ArF) excimer laser light having a wavelength of 193 nm, and as a resist material used for the lithography, various ArF resist materials, which use acrylic resins as a base, have been developed. Moreover, as a lithography technique of the next generation, extreme ultraviolet (EUV) lithography using as a light source, soft X rays having a wavelength of 13.5 nm has been studied, and therefore it is obvious that a pattern size will continue to be reduced, e.g. 30 nm or shorter, in the future.
Along with the above-mentioned reduction of the pattern size, roughness of side walls of a resist pattern, i.e. line edge roughness (LER), and unevenness of a resist pattern line width, i.e. line width roughness (LWR) of the resist pattern have become more significant, which bring concerns that these defects may adversely affect performances of a resulting device. Although various studies have been conducted to inhibit LER and LWR of a resist pattern by optimizing an exposure device, a resist material, and process condition, sufficient results have not been achieved. Note that, the LWR and the LER are related to each other. The LER is improved, as the LWR is improved.
As a method for solving the aforementioned problem, for example, the method of improving LWR and LER is disclosed, and in this method, a resist pattern is treated with an aqueous solution containing an ionic surfactant in a rinsing process, which is performed after a developing process, so as to dissolve the roughness of the resist pattern at the same time as reducing defects (e.g. defects including residues, and deformation of the pattern) caused by the developing process (Japanese Patent Application Laid-Open (JP-A) No. 2007-213013).
Moreover, another method is disclosed in JP-A No. 2010-49247, and in this method an organic coating material, to which a low molecular acidic compound containing a carboxyl group, is applied to a resist pattern that has been developed, and the coating material is then removed to thereby reduce LWR and LER as well as sliming the resist pattern (see JP-A No. 2010-49247).
However, these proposed methods have a possibility to significantly increase values of the LWR, and LER, i.e., significantly increase unevenness or roughness of a resist pattern.
The present inventors have disclosed a resist pattern thickening material that enables precise processing by swelling (thickening) the resist pattern (Japanese Patent (JP-B) No. 3633595, and JP-A No. 2006-259692). In the case where a resist pattern is subjected to a thickening process using such resist pattern thickening material, however, a size of the resist pattern is largely changed. Therefore, it is not suitable for a material for improving LWR, which desirably improves LWR of a resist pattern, without changing a size of the resist pattern more than necessary.
As described above, the techniques of the conventional art have problems that a desirable size of a resist pattern cannot be obtained even though the LWR, and LER are improved, or the values of the LWR, and the LER may be significantly increased, i.e. roughness or unevenness of a resist pattern may be significantly increased.
As a similar method, a resist pattern forming method is disclosed (see JP-A No. 2005-294354), and in this method, after developing, a resist pattern is treated with an aqueous solution containing a certain surfactant, as a rinsing fluid to thereby prevent the resist pattern from falling, but nothing is disclosed about improvements of the LWR, and LER.
Accordingly, it is currently desired to provide a resist pattern improving material that can reduce LWR of a resist pattern without changing a size thereof more than necessary, a method for forming a resist pattern and a method for producing a semiconductor device using the aforementioned resist pattern improving material, and a semiconductor device produced by the aforementioned method for producing a semiconductor device.